1. Field of the Invention
Embodiments described herein relate generally to a cascade refrigeration cycle apparatus comprising a high-temperature-side refrigeration circuit and a low-temperature-side refrigeration circuit.
2. Description of the Related Art
A cascade refrigeration cycle apparatus is available which comprises a high-temperature-side refrigeration circuit and a low-temperature-side refrigeration circuit which share one cascade heat exchanger (intermediate heat exchanger) allowing heat to be exchanged between a refrigerant circulating through the high-temperature-side refrigeration circuit and a refrigerant circulating through the low-temperature-side refrigeration circuit, thus achieving a high compression ratio.
In general, the high-temperature-side refrigerant, used for the high-temperature-side refrigeration circuit, has a higher boiling point than the low-temperature-side refrigerant, used for the low-temperature-side refrigeration circuit. In other words, the low-temperature-side refrigerant has a lower boiling point and a higher pressure than the high-temperature-side refrigerant. Thus, a saturation gas density at the same temperature is lower for the high-temperature-side refrigerant than for the low-temperature-side refrigerant.